The diuretic and saluretic response to the intravenous infusion of a 5% salt solution (5 g of NaCl/m2 of body surface area) was examined in a group of normotensive subjects, in patients with uncomplicated essential hypertension, in normotensive women after toxemia of pregnancy and in subjects with ‘labile’ hypertension, who were normotensive at the time of the study. It was found that the 2 latter groups reacted to the procedure in a very similar manner as the subjects with hypertension, i. e. with a diuretic as well as saluretic response of rapid onset, in contrast to the gradual and much lesser rise in water and salt excretion observed in the normal control subjects. The diuretic response in all 3 experimental groups was more pronounced than the saluretic response. The use of a salt loading test appears to be useful in epidemiological and prospective studies on hypertens